(pathology) A long-term respiratory condition, in which the airways may unexpectedly and suddenly narrow, often in response to an allergen, cold air, exercise, or emotional stress. Symptoms include wheezing, shortness of breath, chest tightness, and coughing.

1954, William Golding, Lord of the Flies

"He kind of spat," said Piggy. "My auntie wouldn't let me blow on account of my asthma. He said you blew from down here." Piggy laid a hand on his jutting abdomen.

Mostly, the microbiome is beneficial. It helps with digestion and enables people to extract a lot more calories from their food than would otherwise be possible. Research over the past few years, however, has implicated it in diseases from atherosclerosis to asthma to autism.